Safety interlock for machine gun barrel



April 25, 1961 P. E. SWEENEY SAFETY INTERLOCK FOR MACHINE GUN BARREL 2Sheets-Sheet l Filed Jan. 7, 1960 PATRICK E. SWEENEY IN V EN TOR.

ATTORNEX April 25, 1961 P. E. s wEENEY 2,981,154

SAFETY INTERLOCK FOR MACHINE GUN BARREL Filed Jan. 7, 1960 2Sheets-Sheet 2 PATRICK E.SWEENEY v INVENTOR.

ATTRNEK i nted States SAFETY rNrERLoCK Fon MAcrnNE GUN BARREL Patrick E.Sweeney, Baltimore County, Md., assignor to Aircraft Armaments, Inc.,Cockeysville, Md., a corporation of Maryland Fired Jam?, 1960, ser. No.1,066

s claims. (ci. s914) This invention relates in general to automaticmachine guns, and more particularly to a safety interlock for perlmitting the barrel ofV a` machinev gun to be quickly lbarrel can beremoved for replacement after a certain period of use. One of theproblems associated with quickly changing the barrel is that of insuringproper head space or distance between thel shoulder in the cartridgechamber of the barreland the bolt block face when the lat-v ter is infiring position. Generallythebarr,el is threaded into the barrelextensionfrequiring gaging of the axial p position of the barrel inorder to insureproper head space before the barrel is locked inposition..l A failure to,pro-` videy adequate headspace can result injamming of the gun, while head space Vin excess of thatv which is propercan result in rupture of al cartridge on firing.l Thus, when a barrel ischanged, it is essential that time be taken to gage the new barreltoinsure the proper amount of head space.

, v It is therefore an object of this invention to provide a Yconnection between barrel and barrelextension which requires merely theaxial insertion and rotation ofthe barrely inthe barrel extension toinsure proper locking of the barrel to the extension and creation of theproper head space.

of is achieved, interengaging lugs lon the barrel andbarextension to afixed depth and rotation of the bairel until ja spring-loaded detentsnaps into place` andV holdsv the barrel at a particularangular positionat which the lugs on'the barrelV and barrelextension cooperate'toprevent,

withdrawal of the barrel. Thelhead space is automatically xed .and allthat is necessary tobe done isto insert and rotate thebarrel through.afsuflicient angle after in.-

in haste to change barrels, the` new` barrelV is notrotated sutlicientlyfor the detent to be eiective! rThis result is Vacxorriplished,byproviding a safety lever on the barrel extension which normally ispositioned in the path of the As a feature of this invention whereby theobject'ther'ef ICC . tailed description thereof that follows may bebetter understood, and in order that the contribution'to the art` maybebetter appreciated. There are, of course, addin tional features of theinvention that will be described VVrelyextension permit insertionof'thebarrel into the barrel hereinafter' and which will also form the subjectof the claims appended hereto. Those skilled in the art will appreciatethat the conception upon which this disclosure is based may readily beutilized as a basis for designing other structures for carrying out theseveral purposes of this invention. It is important, therefore, that theclaims toy be granted herein shall be of sufficient breadth to preventthe appropriation of this invention by those skilled inthe art. p -Y Inthe drawings: l

Figure l is a top sectionalvviewv taken along theV line 1-1 of FigureZand showing a machine gun with the barrel properly. locked into thebarrel extension and the bolt assembly in position for `firing acartridge in the chamber of the barrel. 5 t

Figure 2 is a side sectional View ofthe machine gun shown in Figure l. f

Figure 3 is a top sectional view similarto Figure l but showing thebarrel improperly attached to the kbarrel extension'and the boltassembly held back from itsring position. f n f Figure 4 is a sidesectional view of the machine gun shown in'Figure 3.

Figure 5 is a sectional view taken along the `line 5-5 ofFigure 1andshowing the safety lever. in an inoperative position.

lFigure 6 is a sectional view taken along the line6-6 of Figure 3 and issimilar to Figurey 5 except that parts Vare broken away to show, theksafety lever inoperative position.

Figure 7 is a perspective vView of the forward end of the barrelextension showing the lockinglugs thereon.

Figure V8. is a perspective View of the rear end of the barrel showingthe locking lugs thereon and the cam surface for moving the safetylever.

Referring now to iFigure l, reference numeral iii designates anautomatic machine gun having a receiver 1,1 with aV forward portion 12,a rearward portion i3, and'intermediate portion 1'4. Portion 13 isformed with longitudinally extending guide rails l5, and portion 12 isformed-with bearing surfacel and apertures 17. Portion 14 is providedwith grooves 18 for the reception of accelerator housing '19 upon whichaccelerator Ztl is pivotably mounted at 21,- Acceleratorztl is biased bysprings (not shown) toward wall 22 on receiver 11.

Slideably mounted within portion 13 of receiver 111 is barrel extension23 which hasbearing grooves 2 4 on v each side' (see Figure 7*)`engaged' with rails 15. Bari sertiorria` Because of thesimplicityoftheyabove des :rilj edA connection, it is desirable 'to-prevent Ifiring ofthe gunpi'f, v

bolt assembly carryingv the tiring pin and prevents the firing pin-fromcontacting andiiring acartridge inthe chamber yof the barrel;"The'barrel is provided with Va camavhi'chis engageable withthe leverupon rotation of thebarrelsuchthat' its rotation to the angular positionywhere the ydetent* elfective earns'thev safety levervout of'the-path'of the bolt-assembly. lnjth'is manner, aV cartridge inthe;chamber canbe'iired only` afterthebarrel is prop.-

l erly'hattachedi'to Athe barrel''extensrio'n.v y Y lTli e importantyffeatu'res 'olfrthisf invention lhave 'K @been outlined 'rather ginorder ythat `the l'def t i j y rel extension 23 has a forward portion 25(i,e., the portion to which the barrel is attached) which Yextendsacross the widthofportionlS of receiver 11, andrearwardly l, directedlegs 26 on each side. LegsA Zoyhave ,groovesrll on their outer faces.The inner vfaces of legsf26 contain entire length bolt `assemblylgrooves 27 which extend the ofthe barrel extension. v Y

Bolt assembly 3@ has two main parts: bolt slideval, and bolt block 32,.Bolt slide '31 has flanges 3,3 slideably 'engaged in grooves `27.Beneathilanges 33 is tubular portion 34 having laperture 35incylindrfical spring well 36 through which bolt return spring rod 37passes.

Bolt return spring fhaskone yend lenga'ged against" thel Irearof'receiver 11 (not shown)l and one-end engaged in weil 36 for cn'stamlyingingtit fassembiy :ss-forwardly toward-wallf2.2v of receiverfll,Y1Ab`c ve ange 33V y is ytiring pin holder '39W`hic'h` is providedvwith. a longitu f Y dinaly slot 40, in which'slidejtl Vof,bolt''block132 isj'en- 'gageableJ-Slide 41 fispro'vided with elongatedhole 42f through whichpas'sesffpin 43 attached'to holder '39. In

A 3 this manner, bolt block 32 is connected to bolt slide 31 for limitedrelative movement. Rigidly attached to holder 39 is firing pin 44 whichextends through aperture 45 in bolt block 32 and can project therefromas seen in Figure l. Pivotally mounted on each side of bolt block 32 arelocking latches 46 which are engageable in keeper notches 47 formed inthe inner face of legs 26 of barrel extension 23 when the bolt block isat its forwardrnost position on the barrel extension. I

Bolt block 32 has extractor cam 48 pivotally mounted below aperture 45and biased upwardly toward the aperture. Cam `48 is engageable 4with therim of a cartridge for extracting the same fromjthe chamber of thebarrel when the bolt block is moved rearwardly by bolt slide 31. Cam 48has ears (not shown) which are engageable with extractor grooves 49 onthe inner faces of legs 26 to controlmovement of the cam relative to therest of the bolt block when the bolt block moves relative to the barrelextension. Above aperture `45 is stripper cam 50 which engages the baseof afresh cartridge above and behind portion 25 of the barrel extensionduring forward movement of bolt assembly 30 underthe effect of returnspring 38.

Pivotally mounted on receiver 11 is detent lever `51 having arm 52extending through slot 53 in receiver 11. Lever 51 has aperture 54 inwhich pin 56 can slide transversely, rotation of pin 56 being prevented.Pin 56 has j a portion which is circular (Figure 4) vand a portion whichhas ears thereon (Figure 2). `When pin 56 is in the position shown inFigure l, lever 51 is locked against rotation because the ears on thepin engage corresponding v The chambered end of barrel 60 has a portion64Y of reduced diameter that is connected to an intermediate portion atshoulder 66. Forward of intermediate portion 65 is bearing ring 67 ofthe same diameter as bearing `16 in receiver 11. Bearing ring 67 has`axial recesses 68 which serve to lighten the barrel and prevent`distortion of the barrel due to the heat `generated when the gun iscontinuously fired. Axial slot 69 is formedv in the surface of portion65. Bolt locking lugs 70 and 71 are formed on the free Vend 72 ofthebarrel adjacent chamber 6 2. Lugs 70 and 71 are located 90 on each sideof the location of slot 69 and are thus 180 apart as shown best inFigure 8. Lug 70 hasradial end -faces 72 and lug 71 has radial endIfaces 73 to deiinerlugs which extend circumferentially through`approximately one quadrant on opdirection of lgroove 69 hassemicircular recessV 74 therein.

Projecting beyond the planeof the rear face 75 of thebar-v 23 withrecess 80. Recess 81 is of a diameteri su'iciently large to permitrotation therein `of freejend` 72 `of the barrel. ExtendingVradially/into 4recess Sjltare barrel `extension locking lugs 83.and`84, whichifornilfcontinuations `ofvface 82.flugs83 fand84.are`.oppositely spaced-180 apart and 'larerabout oneV quadrantinglength;` The clearance `between the crests. ofglugsr 33 yanlf84 isV`substantially equal to the diameter'of portion64' on the Vbarrel.` fMounted to one side of the center line of barrel ex- 4 l tension 23 isstop pin 85 which projects radially into aperture 81. Pin 85 is locatedaxially inwardly of face 82 asuiiicient distance so that it engagesrecess 74 in lug 71 on the barrel. Barrel extension 23 has a verticalhole 86 which extends from the top of the barrel extension downwardlyinto recess and aperture 81. The forwardmost edge of hole 86 is rearwardof pin 85 such that it is substantially -aligned with face 75 of thebarrel when shoulder 66 of the barrel abuts face 82 of the barrelextension (see Figures 2 and 4). Safety lever 87 is pivotally mounted inhole 86 on pin 88 that is connected to the barrel extension. Torsionspring 89 coiled around pin 88 has one end attached to the lever and theother end (not shown) bearing on an edge of hole 86. Spring 89 ismounted so that lever 87 is continuously urged to a position shown inFigure 6 where end portion 90 projects into the path of bolt block 32.AThe projection of the bolt block is shown by the phantom lines inFigures S and 6. Hole 86 is large enough so that lever 87 can pivotagainst the action of spring 89 out of the path of bolt block 32 asshown in Figure 5.

The attachment of barrel 60 to barrel extension `23 will now bedescribed.- Barrel 60 is slidably and rotatably mountable in receiver 11because of bearing ring67 and bearing 16. Barrel 60 has another bearingforward of ring 67 that also engages a bearing on the forward end of thereceiver, but these bearings are not shown. Pin 56 is moved in aperture54 in lever S1 such that the latter may manually be moved against springpressure to the position shown in Figure 4. While the lever isdepressed, barrel 60 isinserted into barrel extension 23 by being 'movedaxially (to the left as viewed in Figure 4) with lugs 70 and `71positioned `90" out of alignment with lugs 83 and 84. In this manner,the free `end portion 64 of the barrel can be inserted into aperture 81until shoulder 66 on the barrel abuts` -face 82 on the barrel extension,and lever 51 is heldin theposition shown in Figure 4 by portion 65 ofthe barrel. Because the lugs on the barrel are now interior `to the lugson the barrel extension (see Figure 3), the barrel` can now be rotated90.u until groove 69 opens upwardly. The position of the barrel is 'asshown in Figures 1.and 2 and lever 51 snaps into groove 69. Inaddition,stop pin enters notch 74 in lug 71 and prevents further` rotation of thebarrel ,beyond the point where the lugs on the barrel are directlybehind the lugs on the barrel extension.` In this position, barrel d 60cannot be withdrawnfrom the barrel extension. As

j d tween shoulder 63 in thecharnber (Figure 2) and the fory positesides` of portion 64. The one 4face 73 facing in the i rearward of`the'position fshown in Figure 1. 6U

ward face of bolt block 32,` when the latter is positioned with latches`46 engagedV in keepers 47, defines the head space. Thus, `by simplyinserting and rotating the barrel, the proper head space is achieved.

" Assume now thatthe barrel'is properly attached to thebarrel extensionand thattheV bolt assembly 30gis d Stripper carne 50 on bolt slide 31engages the base of a cartridge as `thehbolt-slide..is drivenforwardbyreturn spring 38. Thecartridge is cammed downwardly by achamberingramp on receiver 11 untilextractor cam 48 is engaged in the extractorgroove injthe cartridge and the bolt block engages the base of thecartridge. Further .forward v movementlof the bolt assembly causes thecartridge to be inserted into chamber 62 by the action of bolt block 32.During `this forward movement, the bolt slide and `boltblock arepositionedrelative to Aeach other as shown best in Figure 3. If safetylever 87 isA in its inoperative positionybolt block 32 drivesthecartridge into the charnp Y ber untilit seats against `shguider 63. lForward movev rnent'of` block 32 ceases as bolt slide` 31 continuesrfor-Ward.movement,simnltaneouslylcamminglatches 461i`nto` j l keepers 47;and causing ring pin 44 to move through the bolt block to strike andfire Vthe cartridge. The bolt assembly is now locked tothe barrelassembly and both recoil together. Recoil of the barrel causes ring 67to impart pivotal movement to accelerator 2.0 against its spring.However, the curvature of the accelerator is chosen so that duringinitial recoil, the portion ofthe accelerator contacting well 36 on theboltslide moves axially through the same displacement as the barrel.This prevents any relative movement between the bolt assembly and thebarrel extension during initial recoil and permits reduction in the gaspressure in the barrel before the cartridge is extracted. As the barrelrecoils further, accelerator 20 causes relative movement between boltslide 31 and the barrel extension storing energy in spring 38.Simultaneously, firing pin holder 3 9 is withdrawn from its cammingposition between latches 46 as pin 43 moves in slot 42 in bolt block 32.Further `movement of bolt slide 31 relative to the barrel extensionfirst causes keepers 47 to cam latches 46 inwardly `toward the ring pinand then causes rearward movethat the barrel is improperly attached tothe barrel exable means for preventing rotationr of said barrel Aawayfrom said other angular position.

3. The combination with a gun barrel having a chamber at one end, abarrel extension having anaperture therein for receiving said'A one endof the barrel, and a bolt assembly slideably mounted on said barrelextension for firing a cartridge in the barrel chambervwhen the boltassembly moves to a certain location on the barrel extensionyof a safetyinterlock for attaching the barrel to the barrel .extension comprising amovable safety lever mounted of said barrel extension, saidsafety leverhaving anoperative position in the path of said bolt assembly movementof they same to vrsaid certain location and preventingthe tiring of acartridge in the barrel chamber, said safety lever having an inoperativeposition out of the path of said bolt assembly for effect-y ing movementof said bolt assembly to said certain location and the firing of acartridge in the barrel chamber, means constantly urging said safetylever to said operative position, locking lugs projecting from said oneend of said barrel, latching lugs on said barrel extension projectinginto the aperture, said lugs being cooperable for tension and thatportion 90 of lever 87 projects into theV path of bolt block 32. Spring38 drives the bolt assembly forwardly causing a fresh cartridge to enterchamber 62. Forward movement ceases when the bolt block strikes thesafety lever. However, bolt slide 3'1 cant not move relative to the boltblock as shown in Figures 3 and 4 because latches 46 are not alignedwith keepers 47. As a result, iiring pin 44 cannot strike and tire thecartridge, and the gun cannot function.

It lcan now be appreciated that with this invention an extremely simpleconnection between a barrel and barrel extension is achieved while atthe same time insuring against accidental ring if the barrel isimproperly con-l nected. l

What is claimed is:

l. In a machine gun havinga gun barrel connected to one end of a barrelextension slideably mounted kin a receiver so that the chamber of thebarrel' is adjacent said`v one end, a bolt assembly mounted von saidbarrel Y extensionfor reciprocatory movement thereon from onev terminalposition adjacent said one end of the barrel extension to another`terminal position remote from said one end, said bolt assembly having atiring pin" thereon for contacting and firing a cartridge in 'thechamber when the bolt assembly moves to said one terminal position; asafety interlock for attaching the barrel tothe barrel extensioncomprising: means to effect insertion` of said barrel intosaid barrelextension only at a given angular position of the barrel relative to thebarrelextension, means to eiect rotation of said barrel after insertionvand prevent its' withdrawal from the barrel extension, stop means tolimit rotation of the barrel so preventing insertion of said one end ofsaid barrel into barrel, said cam means being engageable with saidsafety lever only when said barrel is rotated toward said stop means,rotation of said barrel against said stop means causing said cam meansto move said safety lever froml j operative to inoperative position.

4. In combination: a generally cylindrical gun barrel y having an .axialchamber atone end, said chamber adapt'- ed to receive a cartridge, saidone end having radial extending lug means; a barrel extension Vhavingan-axial aperture at one end sufliciently large to receivel said lugmeans, Vsaid barrel 'extension having lugV means extending radially intothe aperture, the lug means on said barrel extension and barrel beingcooperable to -eiect axial insertion of said end vinto said aperturewhen said barrel has a first angular positionrelative to the barrelexten'-v sion, said lug means being cooperable after said end is *Iinserted in said barrel to yelfect'rotation of said barrel away fromsaidfirst angular position and `to prevent its axial withdrawal, stop meanson said barrelA extension to Y.

` limit rotation of the barrel to `a second'angular position, l

a bolt assembly slideably mountedon said barrel exten` v sion formovement to'an operative position adjacent said y one' end thereon,fsaid bolt assembly having a tiring pin j thereon for contacting andfiring lacartridge, inthe chamber when said bolt'assembly isf-in itsoperative position,

` a safety lever mounted on saidbarrel extension for rnove-l l ment froman operative position to an inoperative posi-V tion, the operativeposition of said lever being in the path ofthe bolt assembly` forpreventing movement of said bolt assembly to its operative position, theinoperative vposition of said'lever being out of the path of the boltthat after its insertion and rotation the barrel has anv.

other angular position different from said given angular v"position,movable means on said barrel extension posi-l tioned in the pathof saidbolt assembly for preventing r movement-of the latter to said oneterminal tposition,

and means on said .barrel for cammin'g Asaid movable means out lofthepath of said bolt assembly uponrota'- assembly vfor Veectingvmovement of. said bolt assembly to its operative position, springmeansconstantly urging said lever to its operativeposition, and cammeans being `fengageable with said levei-upon rotation of said vbarrelytion of'said barrel to the limit determined 'by said stop i "means 'j Y.7. 2. In the machine gun of claim 1*,sele`ct1vely opertowardsaid secondangular position for moving saidlever against v the Iaction of pSaidspring means, movementA Vof said barrel-Pto saidy second angularposition causing movement of said lever to inoperative position.

5.l In a machine gun having a receiver, a member slideably mounted insaid receiver, a bolt assembly slideably mounted'on 'said member forreciprocatory movement tl- 'ward and away from a terminal position,- atiring pin on said. bolt assembly, saidvflringipin being effective when`tl1e bolt assembly ,is atits terminal position, and a barrel having achamber in one end for receiving a cartridge, said barrel beingslideably and rotatably mounted in said receiver; means for connectingthey barrel to the barrel preventing withdrawal of the barrel, detcntmeans fory retainingsaid barrel at said angnlar position, safety levermeans mounted `on said` barrel extension for movement from an operativeposition to an inoperative position, the

operative position of the lever ,preventing ,the bolt assemb1y``fr`ommoving to itsterminal positionI and the firing pin r'from `beingeffectiveto fire a cartridge in the chamber, theinoperative` position ofthe lever :effecting movement of `the-'bolt assembly to its` terminalposition and firing` of arcartridge in the chamber by the firing pin,means constantly yurging said lever to operative position, and cam means`on said barrel engageable with said lever upon rotation of the barrel,'said cam means being etective -to move said lever to inoperativeposition only after said detent means is eiective to retain said barrelat said angular position.

